Proton exchange membrane fuel cell current generation

Due to methanol crossover, Reaction 7.4 accounts for methanol oxidation at both the anode and the cathode, while Reaction 7.5 accounts for oxygen reduction at the cathode. The protons generated at the anode by Reaction 7.4 diffuse across the proton exchange membrane, while the electrons pass as current through the external circuit to reach the cathode, where oxygen is reduced by the protons and the electrons to form water, according to Reaction 7.5. Figure 7.3 shows the difference at the anode between H2/O2 (or air) fuel cell and DMFC. 

The conventional PFSA membranes currently used for PEM fuel cells, such as Nation or other PFSA polymers, show significant conductivity loss at high temperatures due to membrane dehydration [89]. Moreover, in the effort to increase proton conductivity, the proton exchange membranes used in PEM fuel cells are becoming progressively thinner, which can worsen dehydration. Even more of a problem is that when the membrane is thinner, gas crossover becomes an issue, as it not only generates mixed potential—thereby decreasing cell performance—but it also compromises safety. 

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